Study On Processing Technology Of Pumpkin Leaf Powder (MUD)

Pumpkin,a kind of important economic crops in China,is widely distributed in our country with lots of advantages such as high output,easy growth,low production cost,and its annual output is up to 4.1 million t,which accounts for 30% of world yield.The high production of pumpkin at the same time brings rich resources of pumpkin leaves and stems.There is about 30% of crude protein in pumpkin leaves which makes it a valuable and high quality plant protein resource worthy to be developed and utilized.At present,most of the pumpkin leaves have not been used except small amounts for eaten or as a feed resulting in substantial waste.In order to provide technical basis and technical guidance for reasonable utilization of pumpkin leaves,the effects of processing on quality of pumpkin leaves puree were studied.The main conclusions are as follows:Harvest time and leaf area of pumpkin leaves effected the chemical components differently.Leaf area had a greater impact on contents of leaf moisture,vitamin C,protein,fat and crude fiber.With the increase of leaf area,the contents of vitamin C,protein and fat decreased,while the contents of crude fiber,total phenol,and total flavonoids increased.Moisture content was the highest of the second harvest time and the size of 3000 mm~2.Harvest time also effected on the index above,which even made a greater impact on total phenols and flavonoids contents of pumpkin leaves.With the push harvest time,the contents of total phenol,total flavonoids,crude fiber,and fat increased gradually,while the contents of vitamin C decreased.Effects of blanching on the quality of pumpkin leaves were studied by analyzing peroxidase(POD)activity,the contents of vitamin C,soluble protein and oxalic acid and color during steaming blanching,microwave blanching and hot-water blanching.Results showed that POD activity was obviously inhibited by three blanching methods.The relative residual POD activity was decreased to 7.10% in the 60 s by steaming blanching.The hot-water blanching showed that POD activity was influenced more by the blanching temperature,which was significantly inhibited up to 95℃ and decreased to 4.85% at 95℃ for60 s.POD relative residual activity of pumpkin leaves fell to 5.05% by microwave blanching at 480 W for 50 s.Hot-water blanching remained the highest contents of vitamin C and solubleprotein,followed by microwave blanching and steaming blanching.Lower content of oxalic acid,the maximum value of L * and minimum value of a * confirming the best color of pumpkin leaves were obtained by hot-water blanching.Hot-water blanching for 60 s at 95℃is the most appropriate way for pumpkin leaves.The results could provide technical basis for deep processing and utilization pumpkin leaves.In order to investigate the quality of frozen dried pumpkin leaves during processing,effects of blanching,including steam blanching,microwave blanching and hot-water blanching,on the quality of frozen dried pumpkin leaves were studied by analyzing the contents of vitamin C and chlorophyll,color and rehydration ratio.The results showed that the contents of chlorophyll and rehydration ratio of frozen dried pumpkin leaves blanched by hot-water were the highest,and their Δa* value is minimum,i.e.the optimal color.After frozen dring,pumpkin leaves blanched by microwave blanching had highest content of vitamin C.The heating temperature and the thickness of the plate material during freeze drying had significant influences on the contents of vitamin C,chlorophyll,color and rehydration ratio of frozen dried pumpkin leaves.The contents of vitamin C and chlorophyll of pumpkin leaves after hot-water blanching compared with steam blanching and microwave blanching were more sensitive to the condition of freeze drying.The suitable freezing dry condition of the pumpkin leaves was 55℃ and 12 mm thickness of the plate material.The heating temperature,thickness and slitting size were chosen to be the important factors affecting the dehydrated pumpkin leaves,as well as the contents of vitamin C,chlorophyll,rehydration ratio and ΔE of final products.Orthogonal design were employed to optimize the conditions for hot air drying of pumpkin leaves.The optimal conditions as follows: 40℃ of heating temperature,12 mm of thick apple slices and 2400 mm~2 of slitting size.The amount of water,salt,cooking oil,spices and granularity of pumpkin leaf had a significant impact on quality of pumpkin leaves puree.Orthogonal design were employed to optimize the conditions as: pumpkin powder,80 mesh size,the dosage of additives(count as the pumpkin leaves powder),sodium alginate 0.5 g/100 g,granulated sugar,5g/100 g,water 30 g/100 g,salt 25 g/100 g,cooking oil 1.5 ml/g,cooking wine 1.5 ml/g,seasoning 15 g/100 g.